Browsing by Author "Retzler, Andrew J."

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    C-59, Geologic Atlas of Pipestone County, Minnesota
    (Minnesota Geological Survey, 2024) Retzler, Andrew J.; Mayer, Jordan A.; Bradley, Margeurite C.; Chandler, Val W.; Severson, Allison R.; Jirsa, Mark A.; Conrad, Daniel R.; Gowan, Angela S.; Van Berkel, Jordan T.; Francis, Sarah W.
    A County Geologic Atlas project is a study of a county's geology and its mineral and groundwater resources. The information collected during the project is digitized and used to develop maps and database files. The map information is formatted as geographic information system (GIS) files with associated databases. The maps and reports are also reproduced as portable document files (PDFs).
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    OFR14-02, Geologic controls on groundwater and surface water flow in southeastern Minnesota and its impact on nitrate concentrations in streams
    (Minnesota Geological Survey, 2014) Runkel, Anthony C.; Steenberg, Julia R.; Tipping, Robert G.; Retzler, Andrew J.
    This report summarizes the results of a Minnesota Geological Survey (MGS) investigation conducted for the Minnesota Pollution Control Agency (MPCA) designed to support watershed planning efforts in southeast Minnesota. Specifically it provides better understanding of the geologic controls on nitrate transport in the region, including nitrate in groundwater that is the source of baseflow to streams. Nitrate contamination of surface water and groundwater is a long- standing issue in southeastern Minnesota. We focused much of our investigation on an evaluation of nitrate (NO3 ion) transport in the Root River watershed because of the relatively advanced understanding of the karstic conditions in that area. However, the overall scope of the project includes the entire bedrock-dominated landscape of southeast Minnesota. Our results therefore support a broader MPCA watershed planning effort that directly pertains to the Root River, as well as to other watersheds within the Lower Mississippi River Basin in Minnesota.
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    OFR14-04, Hydrogeologic Properties of the St. Lawrence Aquitard, Southeastern Minnesota
    (Minnesota Geological Survey, 2014) Runkel, Anthony C.; Tipping, Robert R.; Green, J.A.; Jones, Perry M.; Meyer, Jessica R.; Parker, Beth L.; Steenberg, Julia R.; Retzler, Andrew J.
    To better understand the properties of bedrock aquitards, we initiated a project that utilizes widely ranging methods to gain insights into the properties of the St Lawrence Formation and adjacent strata of the upper Tunnel City Group (Mazomanie and Lone Rock Formations) and lower Jordan Sandstone. The St Lawrence Formation has been traditionally regarded as an aquitard in the Paleozoic bedrock hydrogeologic system.Our investigation addresses hydraulic properties at site-specific as well as sub-regional (square miles) scales. Specific activities included drilling, testing and instrumentation of a borehole in the eastern Twin Cities Metro area (TCMA), the Afton multilevel system (MLS) hole, that has provided us with detailed multi-level measurements of hydraulic characteristics above, below and within the St. Lawrence Formation. We also analyzed the distribution of fractures in bedrock outcrops, in an effort to understand the controls these fractures might have on borehole hydraulic conditions. Borehole and outcrop scale data are augmented with ground-water tracer experiments that provide horizontal and vertical travel times at the sub-regional scale. Compilation of existing published and unpublished hydraulic and water chemistry data provide additional insights into the properties of the St Lawrence Formation and adjacent units across a wider extent of southeastern Minnesota.
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    OFR15-01, HYDRAULIC CONDUCTIVITY AND HYDROSTRATIGRAPHY OF THE PLATTEVILLE FORMATION, TWIN CITIES METROPOLITAN AREA, MINNESOTA
    (Minnesota Geological Survey, 2015) Runkel, Anthony C.; Steenberg, Julia R.; Tipping, Robert G.; Jansen, Steve; Retzler, Andrew J.
    This report synthesizes a large body of data that provide a better understanding of the hydrogeologic characteristics of the Ordovician Platteville Formation in the Twin Cities Metropolitan Area (TCMA). The carbonate-dominated Platteville Formation plays an important role in the TCMA hydrogeologic system by limiting vertical infiltration of relatively recent water to the more commonly utilized aquifers beneath it. Furthermore, it has been impacted by numerous contaminant plumes, which threaten the water quality in domestic wells and the large number (dozens) of springs along the Mississippi River and its tributaries. Hydraulic conductivity data are synthesized and interpreted across a range of scales, with the recognition of variable user needs. For example, generalized bulk hydraulic conductivity for parts of the Platteville Formation may be useful for modeling water budgets through relatively large areas. In contrast, more site-specific needs such as development of remediation strategies and prediction of flow paths may be facilitated by considering the large range in hydraulic conductivity, measured at a number of scales, and by recognizing the location of fast-flow secondary pore networks as well as key aquitards.